Vending machines are well known and have been in use for over a century. Modern vending machines can be implemented in an electrical and/or mechanical fashion and can vary in size depending on the product they offer, often food or beverage for human consumption. Vending machines provide an advantage in that an attendant is not required in order to sell their products. The products are automatically dispensed upon receipt of the customer's payment. The payment of a product in a vending machine is either in the form of coins and bills, or from credit card transactions. Vending machines provide the advantage where a customer can purchase a product at any time, and restocking of the machine can be done during off peak hours.
However significant problems arise when it is desired to vend hazardous substances and products, such as domestic bottled gas, including LPG. In such situations, use of electricity and electro-mechanical apparatus' within a defined safety zone about the hazardous substance can breach safety standards and regulations established to prevent fire and/or explosion of the hazardous substance.
These problems have been addressed with respect to bottled gas vending, by systems such as those implemented by Sleegers, Siraga, or Vidr which dispense gas bottles via a pneumatic system. The operation of these vending machines via pneumatics allows the machines to operate electricity free in the specified safety zone proximate the gas bottles. However using pneumatics is costly for installation and maintenance, and requires the replacement of the compressed non-volatile gases used to operate the pneumatics.